The present invention relates to fuel control systems for internal combustion engines, and relates particularly to governor control means for fuel injection systems.
Many internal combustion engines normally employ governors which are operative in response to the rpm of the engine for controlling the flow of fuel into the combustion chambers of the engine. Such governors are commonly employed on engines having a fuel injection system whether of the sparked-ignition or the compression-ignition type. Such injection systems, however, are more commonly employed or compression-ignition types of engine such as diesel engines.
One problem with such engines is that under rapid acceleration an objectionable amount of exhaust smoke is normally produced. This is especially so of engines which are supercharged by exhaust-driven superchargers. With such engines, a manual governor control can normally be advanced faster than the engine and supercharger can build up to speed to provide sufficient air to the combustion chambers of the engine to support the complete combustion of the fuel being injected therein during a given cycle. The result is that a large quantity of unburned fuel is expelled from the engine and exhausted as exhaust smoke. This results in a waste of fuel as well as possible pollution of the atmosphere.
Another problem with such engines is that they inherently smoke badly under lug conditions. Lug is that condition when resistance to movement of the engine, or engine load, increases until the engine speed is decreased from that indicated by the governor setting. Under such conditions the engine governor attempts to regain the engine's speed by automatically advancing the engine fuel rack to supply more fuel to the engine. However, due to the reduction in supercharger speed as a result of the reduced engine speed, insufficient air is supplied to the engine to support complete combustion of the fuel.
One technique for overcoming this problem has been to provide fuel control means that is responsive to the manifold pressure of the engine to take over under such lug conditions and control the injection. Such systems are shown, for example, in U.S. Pat. No. 2,767,700 issued Oct. 23, 1956 to John H. Parks, and by U.S. Pat. No. 3,485,228 issued Dec. 23, 1969 to K. W. Updyke et al. Both of these patents are assigned to the assignee hereof.
One problem with this type of approach to the fuel injection control is that starting becomes difficult because of the reduced amount of fuel available to the engine. Such reduction in fuel to the engine also inhibits acceleration of the engine. It is desirable from a fuel economy standpoint that a control system be operative to inject the minimum of fuel necessary for complete combustion during the cycle. However, on the other hand, it is necessary under starting conditions to have an excess of fuel in the system available for the combustion chamber in order to start the engine without undue cranking. It is also desirable under certain conditions to be able to accelerate the engine at a reasonable rate.